Re: core data structure?
Re: core data structure?
- Subject: Re: core data structure?
- From: Jerry Krinock <email@hidden>
- Date: Thu, 9 Sep 2010 11:47:47 -0700
On 2010 Sep 09, at 04:14, Amy Gibbs wrote:
> I didn't really want to save the values as attributes, as I'd like the values to reflect changes to the product prices. I only need to display these in a label onscreen.
>
> Is this what transient attributes are for?
Yes, but before you use transient attributes, be sure to study all their limitations given in the Core Data Programming Guide.
I am not a fan of transient attributes, as you can read here:
http://www.cocoabuilder.com/archive/cocoa/237109-only-one-reason-to-ever-use-transient-properties-in-core-data.html?q=only+reason+transient+attributes#237109
http://www.cocoabuilder.com/archive/cocoa/234791-core-data-fetches-transient-properties-nspredicateeditor-sadness.html?q=only+reason+transient+attributes#234899
Unless you have a user base of millions, or are a fantastic programmer, it's hard to beat today's hard drive prices of less than a dollar per gigabyte. So the smartest solution is often to just leave the "unnecessary" attributes in the persistent store, and start on your next project. Another alternative is to add a regular instance variable to your managed object. Regular ivars still work. Or, in this case, it appears that calculating them as needed and implementing +keyPathsForValuesAffectingXxxxx to make them KVObserveable would work and get you home on time.
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